News Websites Proliferate, Stretching Thin Ad Dollars

Many Generate Revenue by Hosting Conferences

Big profits in online news may be as scarce as buried gold but that isn't deterring journalists and investors from rushing into the sector.

In the past few months, about a dozen companies have announced new ventures related to online news, often in specialized areas such as media or technology. The latest is former Washington Post journalist Ezra Klein, who has been hired to launch a general-news site at Vox Media, owner of the tech...